LSM1303 Animal Behaviour Student Blog : camouflage

Snails – The Camouflage Designer

Feng Chongde — Fri, 21 Mar 2008 12:29:00 GMT

The first image that usually comes to mind when we talk about snails is the sluggish animal that has a brown shell which can easily be noticed along the walkway. Something like what you see on the left.

However, this isn’t the case for all snails! Some species of snails, like The Napaeus barquini, are able to slurp up crusty lichen and apply them with their mouths to paint mounds of the mucky cover-up onto their shells. They are able to deposit lichen material even in the farthest regions of its shell by extending their bodies amazingly far beyond the shell margin, till they look they like this.

Disgusting, I know. However, due to this camouflage layer the outlines of the shell merge optically with the surface of the rock faces, presumably an adaptation to natural enemies such as birds and lizards. This ability to adjust and adapt is very similar to those animals which was mentioned in lecture, like the difference in lycaenid butterflies living at different altitudes.

Never knew that snails could come up with such ingenious ideas, did you?

References:

"Snails As Clever Builders: Active Camouflage In A Snail". Science Daily, 31 Oct 2007.

"Snails Fashion Their Own Camouflage", by Jeanna Bryner. LiveScience, 31 Oct 2007.

Kings of Camouflage

ANG HIAP HOE — Fri, 21 Mar 2008 10:23:00 GMT

While pondering what animal to work on for this assignment, my friend aka Chatter came and approached me on MSN to go for a graduation dive trip. Already at my wits end for this assignment, I still have to face all the pestering and bombardment of her underwater pictures and videos. Well, I decided to entertain her by showing interest in her youtube videos and that “tiny” respect for girls pays off. One of her captures caught my attention and made me realize something. Out of so many diving trips, I have missed something that is not as significant as whale sharks or stingrays but something that can fascinate most of the leisure divers. Judging by the title of this article, I can probably forgive myself for not making my dives more worthwhile.

The thought of camouflaging leads many to think of chameleon which is the most common animal to display fineness art of disguising. However, another expert in this field is the cuttlefish, collectively known as cephalopods. Cuttlefish are soft-bodied marine cephalopods, with a large head ringed by tentacles and an internal cuttlebone. Cuttlefish displays various skills of natural camouflage, sepia ink squirting, jet propulsion and neutral buoyancy. This article shall focus on their amazing skill of camouflaging which surprisingly is used for many purposes.

Camouflaging Colours

Cuttlefish is a master of disguise by utilizing its internal mechanism which is its skin covered with special cells (chromatophores, iridophores and leucophores) that can reflect light in many colours. Refer to the video below for youtube video showing changing colours of cuttlefish.

*my friends’ dive trip video capture of a cuttlefish changing colours rapidly while adopting defensive posture

According to Robert Hanlon of the Woods Hole Marine Biological Laboratory, there are three board categories of camouflage patterns: uniform colour, mottled colour, and disruptive patterns (like stripes and spots). Dr Hanlon even went to the extent to test whether the cuttlefish is able to blend with a black and white checkboard and it turns out that it responds by forming astonishingly sharp-edged blocks of white. What is more astonishing is the fact that cuttlefish is colour-blind although they are able to perceive the polarization of light.

Additional Camouflaging Enhancement Skills

Besides the instinctive skill of changing colours, cuttlefish is able to blend with the surroundings. Researchers have said that cuttlefish is far more superior to chameleon in camouflaging skills as they are able to display spatial learning. They are able to blend into surroundings by forming the same texture as the surrounding environments. Refer to video below for flamboyant cuttlefish camouflaging with change of texture and colour.

Furthermore, they do not just mimic the colours of the surroundings, they are able to disguise by making their arms flat and crinkled and wave them like seaweed. Cuttlefish is well-known for being one of the smartest creatures in the marine world and this kind of behavior may be due to imprinting.

Functional Aspects of Camouflaging

Cuttlefish uses camouflaging for different purposes and the most common purpose is defence and predatory instinct. Refer to video below to look at how cuttlefish camouflages itself under the sand to wait for its prey.

Trickery Mating and Courtship

Cuttlefish also uses camouflaging as a courtship strategy. It’s changing colour ability is able to display sexual deception where they disguise as females to elude from their adversaries before discretely mate with the genuine article.

Conclusion

There is lots of marine life out in a lot of dive sites that is worthwhile to observe. This module and my friend has made me realize that diving is not only about understanding the beauty of the underwater, but it is also about understanding animal before we can discover their hideouts as well as to conserve them.

References

The Biology Refugia. (2008). Secrets of Cuttlefish Camouflage. Retrieved March 21, 2008, from

http://staff.science.nus.edu.sg/~sivasothi/biorefugia/2008/02/secrets-of-cuttlefish-camouflage.html

New York Times- Science. (2008). Revealed: Secrets of the Camouflage Masters. Retrieved March 21, 2008, from

http://www.nytimes.com/2008/02/19/science/19camo.html?_r=2&pagewanted=1&ref=science&oref=slogin&oref=slogin

Tonmo. (2003). Cuttlefish Basics. Retrieved March 21, 2008, from

http://www.tonmo.com/articles/basiccuttlefish.php

Wikipedia. (2008). Cutterfish. Retrieved March 21, 2008, from

http://en.wikipedia.org/wiki/Cuttlefish

Nova. (2007) Mating Trickery. Retrieved March 21, 2008, from

http://www.pbs.org/wgbh/nova/camo/mating.html

A seaweed or sea creature?

OH PEI XIAN CHRISTINA — Fri, 21 Mar 2008 05:50:00 GMT

The next time you step into an aquarium or go scuba diving deep in the seas of Australia, don't miss these graceful sea creatures!

A Leafy Sea Dragon

Native to the seas of South and East Australia, the gentle Leafy Sea Dragon is actually a type of seahorse that lives amongst large floating rafts of seaweed. The leafy sea dragons (Phycodurus eques), is one of the most remarkable examples of camouflage in the animal kingdom. Its mimicry of floating vegetation is remarkable and enables it to forage for food with little chance of being eaten itself.

Mimicry is the ability to blend in to ones surroundings or to look similar to another organism.

The name of the Leafy sea Dragon comes from their appearance, with long leaf-like protrusion all over the body. These leaf-like protrusions are not used for propulsion; they serve only as camouflage. The leafy sea dragon propels itself by its pectoral fin on the ridge of its neck and a dorsal fin on its back closer to the tail end. These small fins are almost completely transparent and difficult to see as they undulate minutely to move the creature sedately through the water, completing the illusion of swaying seaweed and kelp.

Catch a video of leafy sea dragons in the deep seas of Australia!

No wonder they belong to the same family...

The Leafy Sea Dragon belongs to the family species Syngnathidae, along with the seahorse. It is a cousin of the pipefish and a cryptic relative of the weedy sea dragon.

A Weedy Sea Dragon

The seahorse is also a master of mimicry and camouflage. It is able to change its colour rapidly in order to blend into their surroundings and evade predation. Another defense mechanism used is mimicry in which some seahorses have adapted appendages that allow them to hide among algae and corals.

Like the sea horses, male leafy sea dragons are responsible for child bearing. However, instead of a pouch like that of the sea horses, male sea dragons have a spongy brood patch on the underside of the tail where females deposit their bright-pink eggs during mating. The eggs are fertilized during the transfer from the female to the male. The males incubate the eggs and carry them to term, releasing miniature sea dragons into the water after about four to six weeks.

Watch a video of a seahorse giving birth!

Mimicry in other species of animals ...

In fact, mimicry is a very common "trick" used by many other species of animals like the Alcon Blue butterfly larvae for example. The study by David Nash and colleagues from Centre for Social Evolution (CSE) at the University of Copenhagen, Denmark, showed that the Alcon Blue Butterfly larvae mimic the surface chemicals that the ants have on their own brood. The closer the mimicry, the faster they get picked up by ants and taken back to the ant nest and put amongst their own brood.

These larvae are parasites and can be highly destructive. Once they successfully tricked the ants into bringing them back to the ant nests, they eat some of the ant brood and will also be fed by the worker ants. They are also fed in preference of the ants' own brood.

After thoughts...

Mimicry and camouflaging of animals is an interesting aspect of animal behaviour. I’m constantly amazed by the animals’ art of mimicry and camouflaging. Animals' mimicry and camouflaging is to avoid danger and ensure continuous supply of food. In the case of the Alcon Blue Butterfly larvae, its parasitic and mimicry behaviour guaranteed the continuos offspring of the Alcon Blue Butterfly. (Poor ants...)

The Leafy Sea Dragon art of mimicry and camouflaging is essential to ensure its survival in its environment. However, they are constantly threatened by human and nature. Many divers like to keep them as pets. Their soft and unstable body caused them to be easily tossed around in huge storms. These factors have caused their numbers to shrink in recent years.

Hence, the next time you are diving in the sea, keep an eye for these creatures as you may have swam past them without noticing! But, just admire them and don't bring them home yah!

References

http://library.thinkquest.org/12880/seahorse.html

http://seahorse.fisheries.ubc.ca/faq.html

http://biology.kenyon.edu/stures/Compsnelson/seafacts.htm

http://www.bbc.co.uk/nature/programmes/tv/wilddownunder/virtual11.shtml

http://members.cox.net/sandymccaw/Musica_Dolce/leafy%20dragon.htm

http://animals.nationalgeographic.com/animals/fish/sea-dragon.html

www.arkive.org/species/GES/fish/Phycodurus_eques

http://www.divegallery.com/Leafy_Sea_Dragon.htm

http://en.wikipedia.org/wiki/Syngnathidae

http://www.amonline.net.au/fishes/students/focus/seadrag.htm

http://www.divegallery.com/Weedy_Sea_Dragon.htm

http://news.bbc.co.uk/1/hi/sci/tech/7171196.stm

http://youtube.com/watch?v=BPlnqckOPdY

http://youtube.com/watch?v=rku0t40SJqY

Turning Green! Or grey? Or yellow?

CHUAN YELI — Fri, 21 Mar 2008 05:31:00 GMT

"Ahhhhhh! Oh my god!! That stupid chameleon gave me a fright!"

"Huh? Where, where?"

"It just ran past us! It's on the tree trunk now!"

"Huh? I can't see it!"

Have you ever had such an experience before? Personally, I had, many times. As we know, chameleons are well-known for their ability to display different colours within a short time. I always thought that they are really smart to be able to adopt this kind of colour-changing mechanism to blend into their surroundings so as to ward off possible predators, until I started surfing the internet for information about the reptile.

(image from http://news.softpedia.com/news/Why-Do-Chameleons-Change-Color-47360.shtml)

The chameleon is able to change colours via specialized cells, which are called chromatophores, under its outer skin layer. The top layers of the chromatophores consists of red and yellow pigments, while the lower layers consists of blue or white pigments. The messages sent to the chameleon's brain will inform it to alterits pigment cells to suit the current situation. It has a chemical called melanin as well, which primarily darkens it when released.

So, when do chameleons send messages to change their colour pigmentation?
Some researchers still believe that camouflage is one of the main reasons, which is similar in the cases of other animals such as the Golden Tortoise Beetle and the Flounder. However, other studies illustrate, contrary to common beliefs, that it is not true and quite the opposite in the case of the chameleon!

"Because these signals are quick--chameleons can change color in a matter of milliseconds--the animal can afford to make it obvious, as the risk that a predator will notice is limited.This finding means that the evolution of color change serves to make chameleons more noticeable, the complete opposite of the camouflage hypothesis."

- http://www.sciencedaily.com/releases/2008/01/080129125524.htm

Rather, it does so as a kind of communication as well as a form of response to changes in temperature. Although different species of chameleon can change into different colours or differ in the variation of colour change, the basic functions of this useful mechanism is quite consistent. The common situations when a chameleon displays colour changes are:

1) Temperature changes
For example, when it is cold, the chameleon might make itself darker, as darker colours trap more heat.

2) Light conditions
For example, when the chameleon is out in the sun for long, it might enlarge its yellow pigments so as to reflect the bright light away.

3) Mood changes/ Communication
    When two males want to compete with each other, this happens:

"If a male is challenged by another male they both begin by showing their brightest colours - until one figures out the other is going to win and changes to a submissive, dark, 'don't beat me up colour,"

    - Dr Stuart-Fox

Also, when a male chameleon is interested in attracting a female one, it will display striking and bright colours. This kind of courtship technique displays how sexual selection of the chameleon works- the more flashy and colourful, the more attractive a male chameleon is!

Since the main communication tool of the chameleon is through visual cues, colour changes play a most significant role in conveying various messages to other chameleons, such as the desire to mate as mentioned above.

From the video:

Please view this link because I don't know how to embed the video here!

http://www.youtube.com/watch?v=cNPDvsWISx0

I was very amazed at how colourful the male chameleon can become to get to hook up with the female one!

All the information I managed to derive from online sources, I am glad to say, have changed my opinion and knowledge about these small eyed and long-tongued reptiles! And they are so lucky-- they do not have to spend a bundle on new coats!

(image from http://en.wikipedia.org/wiki/Chameleon)

References:

http://library.thinkquest.org/C0115747/

http://www.wildwatch.com/living_library/other-2/chameleon

http://www.youtube.com/watch?v=cNPDvsWISx0

"Chameleon colour not to blend in" by Anna-Marie Lever
BBC News, 29 January 2008.

"Chameleons" by Sharon Katz Cooper. National Geographic, October 2002. Retrieved from http://magma.nationalgeographic.com/ngexplorer/0210/articles/mainarticle.html

PLoS Biology (2008, February 3). Conspicuous Social Signaling Drives Evolution Of Chameleon Color Change. ScienceDaily. Retrieved from http://www.sciencedaily.com/releases/2008/01/080129125524.htm

"Why do chameleons change colour? - It's about mood, temperature and light" By Stefan Anitei.
Retrieved from http://news.softpedia.com/news/Why-Do-Chameleons-Change-Color-47360.shtml

Fat or thin? Depends on who you are of course!

LIM SHIBIN — Thu, 20 Mar 2008 17:42:00 GMT

I stumbled upon a video clip on the fascinating behaviour of an owl on Youtube and decided to find more videos regarding it. Although the video was not taken in the natural habitat of the owl and a great amount of human involvement (especially the sound effects, very anthropomorphic) can be seen, it sparked off my great interest in the tiny owl and led to this blog entry.

Japanese crazy over "funny" owl
(sorry for the lack of subtitles in the video, I can't seem to find another one that can show the behaviour so well)

Photo by Gerhard Theron

After much researching, I finally found out that the owl was a Southern White Faced Scops Owl (Ptilopsis granti). From the family of Strigidae, the Southern White Face Scops Owl is characterised by its distinctive white facial disc with broad black outline, ear tufts and orange eyes. They originate from South of Africa and feed mainly on insects, arachnids, small birds and mammals. They produce a call only at night that sounds like a repeated bubbling ‘pooo’, this probably gave rise to the name of the owl, 'popo-chan', in the video.

It is interesting to note the stark difference in the behaviour of the Southern White Faced Scops Owl when different threats were detected.

1. Flaring its plumage to increase size.
2. Contracting of plumage, stretching of body and showing of side profile to resemble a tree branch.

The behaviour of the owl is based on the cost benefit analysis that animals often rely on in their decision-making. Is it more advantages for it to get into a defensive mode or simply camouflage itself? This all depends on who the opponent was.

As seen in the video, the owl chose get into an aggressive mode when it saw the slightly larger barn owl. The Southern White Faced Scops Owl in the video raised its wings high and pumped up its plumage to increase its volume. This can be seen to be a form of warning to the perceived threat. The threat falls under the range whereby an aggressive stance can be more advantages, hence the owl’s behaviour.

On the other hand, with the vastly larger Eagle Owl (please correct me if I’m wrong), the costs involved were too great and the Southern White Faced Scops Owl decided to camouflage itself as a tree branch. This is done so by stretching their body and contracting their plumage, as well as facing their threat with their side profile. This effectively reduces the size of the owl and in turn camouflages it.

Similar Behaviour in Screech Owls

Other species of owls also use the same method of disguise to hide it, sometimes even with their eyes closed, as mentioned and shown during lecture previously. Further research reveals that the concealing posture is also used by the Screech Owl. (Follow link to the relevant article.)

The Screech Owl (Otus asio) was also found to use the same ways as the Southern White Faced Scops Owl to camouflage it, as described in the quote below:

“The owl immediately twisted its body sideways to the sparrow, raised the front margins of the wings slightly and held the rear margins tightly against the back, at the same time compressing the body plumage and so presenting a very narrow silhouette as seen from the sparrow’s position.”

One main difference can be seen from the Southern White Faced Scops Owl in the video, and the description of the Screech Owl’s behaviour. The latter concealed away from sparrows that are very much smaller than itself. It was also mentioned in the article that the Screech Owl did not pay attention or conceal itself from noisy children and dogs that passed by it. Was the owl afraid of being mobbed by the sparrows? Or does the Screech Owl assume this posture in the presence of prey?

As we can see, the same behaviour can mean very different things to even similar species of animals. Hence there is a need to dig deeper in order to gain a better understanding about animal behaviour.

P.s.: I hope this entry will motivate readers to read up more about the fascinating owls!

References:

Wm. L. Putman, 1955. Use of Concealing Posture by a Screech Owl. The Auk, Vol. 75, No. 4. (Oct., 1958), pp. 477-478.

Perrone, M.J., 1981. Adaptive Significance of Ear Tufts in Owls. The Condor, Vol. 83, No. 4. (Nov.), pp. 383-384.

Ecopains d'abord. (2008). Southern White-faced Scops Owl. Retrieved March 20, 2008, from http://www.oiseaux.net/birds/southern.white-faced.scops-owl.html.

Siyabona Africa Travel. (2008). Kruger National Park: Scop Owls. Retrieved March 20, 2008, from http://www.krugerpark.co.za/africa_scops_owl.html.

BirdLife International (2007) Species factsheet: Otus leucotis. Retrieved March 20, 2008, from http://www.birdlife.org.

World Owl Trust. (2008). Southern White-faced Owl Ptilopsis granti. Retrieved March 20, 2008, from http://www.owls.org/Species/ptilopsis/southern_white_faced_owl.htm.

Video Source:

Retrieved on March 20, 2008, from http://www.youtube.com/watch?v=ChTsGDPcCdY

Photograph Source:

Retrieved on March 20, 2008, from http://birdquest.net/afbid/birdspecies.php?func=view&slideno=9&af_bs_id=815.